Device for recovering heat from wastewater, thermal system including such a device, and method

ABSTRACT

This heat recovery device is of the type comprising a vat for holding wastewater and a heat exchanger comprising at least one heat exchange plate comprising two opposite faces and an inner pipe for circulation of a heat transfer fluid between the two surfaces. According to one aspect of the invention, the or each plate is arranged in a heat exchange compartment of the vat so that the wastewater circulates substantially vertically from bottom upwards along the two opposite faces of the or each plate between an inlet of the heat exchange compartment located in the lower portion and an outlet of the heat exchange compartment located in the upper portion. Application to thermal systems with heat pump.

The present invention concerns a device for recovering heat from wastewater, of the type comprising a vat for holding wastewater and a heat exchanger having at least one heat exchange plate comprising two opposite surfaces and an inner pipe for circulation of a heat transfer fluid between the two surfaces.

Said heat recovery devices are used for example in a thermal system including a heat pump to bring the heat recovered from the wastewater to the refrigerant of the heat pump and thereby improve the yield thereof.

DE 32 14 357 describes a device of this type comprising cylindrical heat exchange plates, arranged concentrically so that the wastewater circulates radially from inside to outside alternately passing above and below the plates.

It is one objective of the invention to propose a simple heat recovery device allowing efficient heat recovery without perturbing the flow of wastewater.

For this purpose, the invention proposes a heat recovery device of the aforementioned type, in which the or each plate is arranged in a heat exchange compartment of the vat so that the wastewater circulates substantially vertically from bottom upwards along the two opposite surfaces of the or of each plate between an inlet of the heat exchange compartment located in the lower portion and an outlet of the heat exchange compartment located in the upper portion.

According to other embodiments, the heat recovery device comprises one or more of the following characteristics taken alone or in any possible technical combination:

the heat exchanger comprises at least one group of plates arranged in one same heat exchange compartment of the vat;

the inner pipes of the plates of one group of plates, arranged in one same heat exchange compartment, are in parallel fluid connection so that they can be fed with heat transfer fluid;

the plates of one group of plates are arranged parallel to one another, each pair of adjacent plates defining a throughway between their opposite surfaces for the circulation of wastewater;

the vat comprises a baffle to force circulation of the wastewater downwardly towards the inlet of the or of each heat exchange compartment;

the vat comprises at least one decanting compartment comprising at least two baffles forming a siphon upstream of the heat exchange compartment;

the vat comprises two side walls that are substantially planar and parallel delimiting between them an inner volume extending along a longitudinal direction between the inlet and the outlet of the vat, the or each plate extending transversally between the two side walls; and

the vat is of general parallelepiped shape.

The invention also concerns a thermal system comprising a heat pump including a compressor, a condenser, a pressure reducer and an evaporator connected in series via a heat pump circuit for the circulation of a refrigerant, the evaporator also being connected to a heat recovery device according to any of the preceding claims for the transfer of the heat recovered from the wastewater towards the refrigerant of the heat pump.

The invention further concerns a method for recovering heat from wastewater, in which the wastewater is caused to circulate substantially vertically from bottom upwards along two opposite surfaces of a heat exchange plate comprising an inner pipe for the circulation of a heat transfer fluid between the two opposite surfaces of the heat exchange plate.

According to one embodiment, the wastewater is caused to circulate substantially vertically from bottom upwards along two opposite surfaces of each heat exchange plate of a group of heat exchange plates each comprising an inner pipe for the circulation of a heat transfer fluid between the two opposite surfaces of the heat exchange plate, the exchange plates having parallel fluid connection for supplying heat transfer fluid thereto.

The invention and its advantages will be better understood on reading the following description given solely as an example and with reference to the appended drawings in which:

FIG. 1 is a schematic view of a heating system with a heat pump integrating a heat recovery device according to the invention;

FIG. 2 is a longitudinal section view of the heat recovery device along II-II in FIG. 3; and

FIG. 3 is a cross-sectional view of the heat recovery device along II-II in FIG. 2.

The thermal system 2 illustrated in FIG. 1 comprises a heat pump 4 and a heat recovery device 6 to recover heat from wastewater, and a transfer circuit 7 for transferring the heat recovered by the heat recovery device to the heat pump 4.

The heat pump 4 allows the transfer of recovered heat by means of the heat recovery device 6 towards an application requiring the supply of heat such as a heating system of a dwelling, a heating system for a swimming-pool, a system for heating household water . . . .

The heat pump 4 comprises a compressor 8, a condenser 10, a pressure reducer 12 and an evaporator 14, connected via a heat pump circuit 16 for the circulation of a refrigerant. The heat pump circuit 16 forms a closed loop for the circulation of the refrigerant passing successively in the compressor 8, the condenser 10, the pressure reducer 12 and the evaporator 14 and then returning to the compressor 8.

The heat recovery device 6 comprises a vat 18 holding the wastewater and a heat exchanger 20 arranged in the vat 18.

The vat 18 is located in a wastewater evacuation circuit through which the wastewater E passes, derived for example from a collective or individual dwelling.

The transfer circuit 22 allows the circulation of a heat transfer fluid. It comprises piping connecting the exchanger 20 with the evaporator of the heat pump 4 so as to form a closed loop 23 successively passing through the heat exchanger 20 and the evaporator 16, and a pump 24 to force circulation of the heat transfer fluid that is arranged in the closed loop 23 between the exchanger 20 and the evaporator 14.

The transfer circuit 22 further comprises a by-pass 26 to bypass the exchanger 20, that is fed in the closed loop 23 between the evaporator 14 and the exchanger 20 and leads to between the exchanger 20 and the pump 24, and a three-way control valve 27 to control the circulation of heat transfer fluid in the exchanger 20 and/or in the bypass 26.

The transfer circuit 22 comprises a temperature sensor 28 arranged at the inlet of the evaporator 14 to detect the temperature of the heat transfer fluid entering the evaporator 14. The sensor 28 is connected to the control valve 27 controlling the latter in relation to the measurement signal provided by the sensor 28.

The transfer circuit 22 comprises a regulating reservoir 29 connected to the loop 23 between the control valve 27 and the pump 24.

In the illustrated example, the condenser 10 of the heat pump 4 is crossed by a heating circuit 30 of the heating system of a dwelling, in which a heat transfer heat transfer fluid circulates e.g. water. In other applications, the condenser 10 is crossed by a gas e.g. air for a heating system using the forced circulation of hot air.

In normal operation, the refrigerant of the heat pump 4 circulates in the heat pump circuit 16 under the action of the compressor 8. It successively passes through the compressor 8 in which it is heated by being compressed, the condenser 10 in which it transfers calories to a heat source (in this case the heat transfer fluid of the heating circuit 30) the pressure reducer 12 in which it expands by cooling, then the evaporator 14 in which it collects calories derived from a cold source (here the calories recovered by the heat recovery device 6 and transferred by the transfer circuit 22).

In normal operation (bypass closed), the heat transfer fluid of the heat recovery circuit 22 circulates under the effect of the pump 24 successively passing through the heat exchanger 20 in which it takes up calories from the wastewater, then the evaporator 14 in which it transfers calories to the refrigerant of the heat pump circuit 16. The heat transfer fluid of the heating circuit 30 circulates in the condenser 10 taking calories from the refrigerant of the heat pump circuit 16.

The control valve 27 is commanded in relation to the inlet temperature of the evaporator 14 so that part of the heat transfer fluid bypasses the exchanger 20 to maintain the temperature of the heat transfer fluid at the inlet to the evaporator 14 within a temperature range allowing the satisfactory functioning of the heat pump 4, for example at a temperature of between 23° C. and 25° C.

Such as illustrated in FIGS. 2 and 3, the vat 18 is of general parallelepiped shape. It comprises two end walls 32 (FIG. 2) spaced along a longitudinal direction L and extending transversally, two side walls 34 (FIG. 3) spaced transversally and substantially parallel to the longitudinal direction, and a bottom 36 delimiting an inner volume of the vat 18.

In the remainder of the description, the terms <<upper >>, <<lower >> and <<vertical >> are to be construed in relation to the vat in position of use, such as illustrated in FIGS. 2 and 3. The longitudinal direction L is substantially horizontal.

The vat 18 comprises an inlet 38 for the wastewater arranged on one end wall 32, and an outlet 40 for the wastewater arranged on the other end wall 32. The inlet 38 and the outlet 40 are located in the upper portion of the vat 18, i.e. in the vicinity of the upper edges of the end walls 32.

The vat 18 comprises baffles 42 arranged transversally between the side walls 34 and delimiting within the vat 18 a decanting compartment 44 for the wastewater, and a heat exchange compartment 46, the wastewater successively passing through the latter. The heat exchange compartment 46 is arranged downstream of the decanting compartment 44 in the direction of circulation of the wastewater between the inlet 38 and the outlet 40.

The decanting compartment 44 comprises a decanting siphon formed of two baffles 42 delimiting a downward section 48 extending from the inlet 38 towards the bottom 36, and an upward section 50 rising from the bottom 36 towards the upper portion of the vat 18.

The decanting compartment 44 comprises an outlet section 52 formed by a third baffle 42 and descending from the upward section 50 of the siphon towards an inlet 54 of the heat exchange compartment 44 located in the lower portion, adjacent to the bottom 36.

The vat 18 comprises a filter 56 extending through the upward section 50 of the siphon, in the vicinity of the upper end thereof.

The exchanger 20 is arranged in the heat exchange compartment 46. It comprises a group of exchange plates 60, each of substantially planar and parallelepiped shape. Each plate 60 comprises two opposite surfaces 62 (FIG. 2) and an inner pipe 64 (FIG. 3) for the circulation of heat transfer fluid, making its way between the opposite surfaces 62.

Each exchange plate 60 has a lower edge 66 spaced distant from the bottom 36, and an upper opening 68 for the circulation of wastewater through the plate.

Each exchange plate 60 extends substantially vertically and transversally between the side walls 34. As illustrated in FIG. 3, each exchange plate 60 has its side edges in contact with the side walls 34.

The exchange plates 60 are spaced away from each other and, together with the end walls 32 and the baffle 42 delimiting the heat exchange compartment 46, define parallel circulation throughways for the wastewater from the inlet 54 of the heat exchange compartment 44 to the outlet thereof located in the upper portion, and which here is the outlet 40 of the vat 18.

The exchanger 20 comprises a feed pipe 70 via which the heat transfer fluid arrives, and an evacuation pipe 72 through which the heat transfer fluid leaves. The inner pipe 64 of each of the exchange plates 60 arranged in the same heat exchange compartment 46 is fed by the feed pipe 70 and leads into the evacuation pipe 72. Therefore the inner pipes 64 of the exchange plates 60 arranged in the same heat exchange compartment 46 are in parallel fluid connection for the circulation of a heat transfer fluid.

The bottom 36 comprises drainage openings 74, one at the bottom of the decanting compartment 44 and the other at the bottom of the exchange compartment 46.

The vat 18 comprises a drainage circuit 75 to recover any deposits at the bottom of the vat 18 via the drainage openings 74 and to re-inject the wastewater collected with the deposits downstream of the vat 18. The drainage circuit comprises a valve 76 controlling each drainage opening 74, evacuation piping 78 connecting the evacuation openings 74 with a storage tank 80, a return pipe 82 connecting the storage tank 80 with the outlet 40, and a pump 84 arranged on the return pipe 82.

When in operation, the wastewater arrives in the vat 18 via its inlet 38 with more or less regular flow. It circulates through the vat 18 under the siphon effect caused by the baffles 42. It circulates firstly in the decanting compartment 44 which allows turbulence to be set up to homogenize the temperature and free the wastewater of elements in suspension. These remain in the form of deposits on the bottom 36, in the elbow formed between the downward section 48 and the upward section 50, under gravity. The filter 56 allows the filtering of any residual elements.

The outlet section 52 allows the wastewater to return down to the bottom 36, to flow over the exchange plates 60 from bottom upwards.

In the exchange compartment 46, the wastewater circulates substantially vertically from bottom upwards along the two opposite surfaces of each exchange plate 60, and then leaves the vat 18 by circulating towards the outlet 40 through the openings 68.

Regularly, the opening of the valves 76 of the drainage circuit 75 allows the evacuation of deposits formed at the bottom 36, chiefly at the bottom of the decanting compartment 44, and possibly at the bottom of the exchange compartment 46. The deposits are collected in the storage tank 80, the wastewater being re-injected downstream of the vat 18.

The heat recovery device 6 allows circulation of wastewater with limited pressure loss, without perturbing the flow thereof, and also allows efficient heat exchange between the wastewater and the heat transfer fluid circulating in the exchange plates 60.

The decanting compartment allows homogenization of the wastewater and the removal of elements in suspension, which promotes subsequent heat exchange.

The feeding of the inner pipes 64 of the exchange plates 60 and the circulation of the wastewater in the same direction along the two surfaces of each exchange plate 60 improve the efficacy of the exchanger 20.

The shape of the vat 18 and the arrangement of the exchange plates 60 allow efficient heat exchange in a reduced volume. The width of the vat as measured between its side walls 34 is preferably less than 90 cm, in particular less than 60 cm. This facilitates its installation in individual swellings, in particular for passing of the vat 18 through doorways.

Optionally, the vat may comprise several exchange compartments arranged in parallel or in series, the heat exchanger comprising a group of exchange plates immersed in each exchange compartment.

The heat recovery device can be used to supply heat to a heat pump or to any other type of system for the production of heat. 

1-11. (canceled)
 12. A heat recovery device for recovering heat from wastewater comprising a vessel for the retention of wastewater and a heat exchanger having at least one plate including a two sided heat exchange and an opposite inner pipe for circulating a heat transfer fluid between the two sides, wherein each plate is disposed in a heat exchanger compartment of the tank so that the wastewater flows substantially vertically from bottom to top along both sides of the heat exchanger or opposite of each plate between an inlet of the heat exchanger located at the bottom and an outlet of the heat exchanger compartment located at the top.
 13. The heat recovery device according to claim 12, wherein the heat exchanger includes at least one plate arranged in the same compartment as the heat exchanger compartment of the tank.
 14. The heat recovery device according to claim 2, wherein the inner pipe and the plates of a group of plates are arranged in the same heat exchanger compartment and are connected in parallel to fluidly supply coolant.
 15. The heat recovery device according to claim 13, further comprising a group of plates arranged parallel to each other, each pair of adjacent plates defining between their faces a flow passage for receiving wastewater.
 16. The heat recovery device according to claim 14, further comprising a group of plates arranged parallel to each other, each pair of adjacent plates defining between their faces a flow passage for receiving wastewater.
 17. The heat recovery device according to claim 12, wherein the tank includes a baffle to force a flow of sewage down to the entrance of the heat exchanger compartment.
 18. The heat recovery device according to claim 17, comprising at least one settling compartment comprising at least two baffles forming a siphon upstream of the heat exchange compartment.
 19. The heat recovery device according to claim 12, wherein the tank includes two side walls substantially planar and parallel to each other defining an internal volume extending in a longitudinal direction (L) between the input and out of the tank, and each plate extending transversely between the side walls.
 20. The heat recovery device according to claim 12, wherein the tank has a generally parallelepiped shape.
 21. A heat transfer system including a heat pump comprising a compressor, a condenser, a regulator and an evaporator connected in series with a heat pump for moving a refrigerant, the evaporator is also connected to a heat recovery device according to claim 12 for the transfer of heat recovered from waste water to the refrigerant moved by the heat pump.
 22. A method for recovering heat from waste water, the wastewater being circulated substantially vertically from a bottom area to a top area along two opposite sides of a heat exchanger plate including a conduit for internal circulation of a heat transfer fluid between the two opposite sides of the plate heat exchanger.
 23. The method of claim 22, which circulates the wastewater substantially vertically from the bottom area to the top area along two opposite sides of each heat exchanger plate of a group of heat exchanger plates, each with an internal pipe for circulation of a coolant between the two opposite sides of the heat exchanger plate, each of the heat exchanger plates being connected in parallel for supplying coolant. 